Abstract Core C is necessary for the following reasons: (i) requirement as outlined in all Projects for centralized imaging with each Project benefitting from high-resolution, state-of-the-art, fluorescent microscopy; and (ii) strong demand for functional studies to quantify microscopic and organ-level endothelial and alveolar epithelial permeability in the murine lung under normal and pathophysiological conditions (e.g., inhaled LPS, cecal ligation and puncture, intratracheal Pseudomonas aeruginosa, and ?double hit? lung injury models). The physiological support component of Core C will provide standardized methods for quantification of lung vascular (Kf,c and Evans blue albumin tracer methods) and alveolar permeability (instilled tracer PS) in wild type and knockout mouse models or after gene delivery via liposomes. The imaging support component of Core C will provide investigators with resources and expertise for live cell and fixed specimen fluorescence, confocal, and two-photon microscopy as well as state-of-the-art facilities for intravital microscopy of the murine lung, important for cell tracking studies proposed in all Projects. Also, Core C will provide assessment of expression of fluorescent or tagged proteins by fluorescence and confocal microscopy. Professor Jahar Bhattacharya, an authority on intravital lung imaging, will serve as consultant to this aspect of the Core function. In summary, the centralized physiological and imaging services offered by Core C will be needed by all Projects in this Program; as such it is indispensable for the overall success of the Program.